Thread: bevel up planes replacement blade 38 or 50 deg bevel

Derek Cohen recommends getting a 25-degree iron and putting a high angle microbevel on it - easier than honing the full bevel at the high angle. I did this and it works well. No need to buy the higher angle iron.

Neither.

This is another broken record. Sorry ...

If you wish to camber the blade - and all blades for bench planes require some camber in my opinion - then you need to only use blades ground to 25 degrees, and add the bevel angle via a secondary bevel.

Why? Because attempting to camber a 50 degree primary bevel has too much steel to remove. It will be impossible to camber.

And, no, clipping the corners instead of cambering is not the same thing.

Article: The secret to cambering Bevel Up plane blades

Regards from Perth

Derek

I'd like to do a bit of a straw poll:

1. How many of you out there regularly use 38* bevels on BU planes for planing any significant areas?
2. Of those who have bought a second blade, how often do you actually change it?

I suspect that there are few people in the first category & fewer in the second.

I'm not as evangelical about cap-irons as D.W. - I'm not convinced a tight-set cap-iron on a standard pitch BD plane solves ALL problems in ALL woods, but by golly, it can usually make a very good fist on all but the worst of the worst! As I've said before, there are some of our woods that I find respond better to my 60* infill, so it's nice to have that back-up occasionally, but I could count the number of times per year I have it out on one hand. More than once I've thought about getting rid of it to make more room in my over-crowded tool chest, but then along comes a job where it beats all comers, so it gets another reprieve. But most of the time, it's just so much easier & more fun pushing a well set-up standard-pitch plane through any wood.

Call me a pig-headed old reactionary if you wish, but I simply cannot see the sense in trying to make a high-angle cutter by cranking up the bevel on a BU plane to an absurd angle. Besides the extra effort a high cutting angle creates, you are trying to force something that resembles the toe of my boot into a very resistant surface (the sort of woods you are likely to use it on are invariably hard). I suspect you will get tired of it all (in every sense of the word), in short order, if you are tackling anything larger than a box top.

If you must have a high-angle plane, get yourself a HNT (or make one). Leave the planes you use most often set up & optimised for what you do with them 80-90% of the time, & get out the other when you think you need it. I reckon you'll be a much happier chappie.

Just an opinion, and there will be many others......

Cheers,

Ian, I would argue that the 38 degree blade (=50 degrees cutting angle) is for countries with mildly hard and/or interlocked grain. The 50 degree blade (=62 degree cutting angle) is for countries, such as Australia, where we have significantly hard and interlocked grain.

Recall that Rob Lee would visit here a great deal about 15 or so years ago. He and I have been good friends a long time, and I have posted on forums about Australian timbers around the world for many years. It would not surprise me that Rob was influenced by our experiences, and so produced the 50 degree blade. On my adventures on forums in the USA and UK, few woodworkers there have needed more than a 50 degree cutting angle. 60 degrees is considered extreme.

HNT Gordon planes are an excellent choice for a high angle cutter. They are low planes and have a low centre of gravity. Bailey planes, such at Stanley and, especially, LN (who offer high angle frogs), have a high centre of effort, and this makes them harder to push as the cutting angle increases. See my articles on Centre of Effort for fuller explanation: Commentary

Now BU planes are the best at low centre of effort. This makes a significant difference when it comes tonusing high cutting angles. They end up more ergonomic. I love the HNT Gordon planes I have used for longer than Veritas BU planes, but the Veritas would be my first choice for a high cutting angle.

I do not have 38 degree blades. For me it is the extremes where BU scores. So 25- or 50 degree bevels. Only 25 degree primary bevels.

I do use BD planes more these days, ever since I became a convert to the chipbreaker. However I do still use BU a fair amount. They remain very viable, but the chipbreaker is a game changer when set correctly. I am tempted to post about this, how it came to be, but we would wander off topic.

Regards from Perth

Derek

Derek 'ol buddy, I think you missed my point. I wasn't disputing that the high bevel angle on a BU blade works to give you a very high cutting angle, my point is I reckon it's the wrong way to go about it! You achieve the high cutting angle at the expense of "sharpness" of the cutting edge. You are simply further increasing the effort a high angle adds by "dulling" the cutting edge. Raising a BU blade to 62, you still have the same blade bevel of 25 to 30 degrees (whatever your preference & sharpening technique dictates). My argument is that this will penetrate the wood & separate the fibres more readily than an edge bevel of 38*.

I'm not anti-BU planes, I have several, and they do the jobs I keep them for very well, but I doubt I will ever be tempted to increase any of their blade bevels to 38 degrees. It's a means to an end if you have no other, but I do....

Cheers,

Ian, the point you make about "sharpness" is interesting. I would go so far as saying that you are correct, however it would be about answering and agreeing with you on one point, and there other other factors that make up the whole. I think that this is why you thought I had missed the point in your first post (and, of course, I may still be doing so!).

I know that we are generally in tune much of the time, so I hope this is not telling you how to suck eggs.

The comparison of BU vs BD is complicated. On the one hand we have the very fact that you point out, that the more acute an angle, the sharper it is. Conversely, as the cutting angle increases (towards 90 degrees), so the cutting action becomes more one of scraping than slicing. Why is this important? Because, taking this literally, the surface produced by a scraper is different from the surface of a hand plane. The lower the cutting angle, the clearer the surface. 60-degree cutting angles should not leave a clear surface. But they do. In practice, the theory does not filter through. I can get a reflective surface from high cutting angles. We have all been able to demonstrate this. So we argue that sharpness counts. This leads to the second factor ...

The second argument is that a blade's edge on a high cutting angle will last longer in a BD plane, where the bevel may be 30 degrees, compared to a BU plane, where the edge needs to be 50 degrees. The argument may be that the 30 degree blade is more acute, and that there is more leeway to dull than the 50 degree blade, which will round over sooner (as it is closer to round already). This is a logical assumption and, again, it does not hold water. There are two factors involved ...

The first factor is that the 50 degree bevel is much stronger than the 30 degree bevel. This effects the impact resistance of the edge.

The second is that the 30 degree bevel is going to outlast when abrasion resistance is involved. Actually, not only does steel type and wood abrasiveness play a big part here, but so does bed angle ...

What my research into shooting end grain demonstrated to me is that a low bed (BU) plane experiences far less stress on the blade's edge than that on a higher bed plane. In particular, I compared a Veritas shooting plane (12 degree bed, with 25 degree bevel) against a Lie Nielsen #51 plane (45 degree bed, with both 25- and 30 degree bevel angles), using both A2 and PM-V11 steels on both planes. In the first instance, the lower bed angle of the Veritas outlasted the higher bed angle of the LN by the proverbial mile. Just no competition. I have repeated these result on a number of occasions.

The second issue is steel composition, and we all know that answer: PM-V11 and M4 (even M2) will outlast A2 by a factor of two, as will A2 outlast O1.

So what about HNT Gordon? I know Terry has made a few videos arguing the merits of BD. Actually, I am not altogether in disagreement with him - for example, the BU orientation does expose the weakness of the wear bevel reducing the cleanliness of it edge. However, that is a simplistic answer, since other factors come into the reasons we choose one plane over another. For one, HNT Gordon planes aside (I really like mine and post recommendations for them around the globe), BD planes with high cutting angles - especially the Bailey designs - have high centres of effort, that is, their force vectors see an increase in resistance as the cutting angle increases.

The HNT Gordon planes have a low-ish centre of effort, and this makes them easier to push. Bailey planes with high cutting angles are horrible. With a high centre of effort, they feel heavy and stodgy. I prefer smaller smoothers, such as a #3 size. The LN #3 I have was originally purchased with the highest angle from LN, the 55 degree. I hated it as it was so hard to push, plus the cutting angle was not high enough to prevent tearout. And so the plane lived on a shelf for a few years. When I began using the chipbreaker, the frog was swapped for a 50 degree. This worked but it was a chicken-half-measure between chipbreaker and high angle. I took a deep breath and bought the 45-degree frog. With a closed chipbreaker, the plane is wonderful. I added a Veritas PM-V11 blade, and it is sublime.

As you would may recall, from the articles, I have a 40-degree bed Veritas Custom #7 and a 42-degree bed Custom #4. I did get 50 degree frogs for these planes, but they were used once (to try them out) and have lived on the shelf ever since.

The only reason these planes work (and very well) on the interlocked hardwoods with which I work is the chipbreaker, which gets set tight. The 40 degree frog is about as low as I would ever go, as it is pushing the boundary of clearance angles. The 42 degree is pretty safe. But ... if anyone plans to get something in this range, they had better be good at setting the chipbreaker! They are essentially Bailey designs and, as such, are vulnerable to the same issues with high angle beds. I chose to get the bed as low as possible to reduce the centre of effort (which is not the same as centre of gravity, but are in the same category).

I'd better end here as I am sure everyone's eyes are glazing over. This has been an unusually long reply, but I consider that you, as a long time friend, are worth the time and effort. I hope that some of it makes sense, and that you realise I was not contradicting you, nor missing your point, but adding a different perspective.

Regards from Perth

Derek

Well, thankyou Derek, that was indeed a thorough reply.
There are a few technicalities I would like to debate further sometime, but I think it would be best done across the table, with a good glass of red in hand to lubricate the thought processes..

I get the impression that we would both agree that:
1) As a general principal, a standard-pitch plane with a good blade & well-fitted cap-iron is likely to do a very good job about 95% of the time or possibly more. It gives the best return for effort, & probably the best blade-edge longevity.

2) Sometimes, a 60 degree BD blade will do a better job, but at the expense of more effort, and the blade will likely dull faster than the same blade would used at 45*.

3) BU planes can certainly do some things noticeably better than most BDs, (like shooting end-grain).

And all of these depend at least to some extent on the operator and the actual wood being worked.....

Cheers,

One of the reasons that I want to buy a replacement plane iron is that my #7 BU plane came with an A2 blade and I am keen to lay my hands on a PMV-11 iron. I might as well buy a higher bevel iron while keeping the 25° iron for mitre and end grain use.

It seems that 38° is a good compromise and I can always put on a micro-bevel if I want to.

In the discussions. I could see that the way that BU plane deals with difficult material by lifting the effective cutting angle while keeping the relief angle constant at some 12°. On a BD plane, the effective cutting angle is set at 45°, but one could tries to reduce tearing by reducing the relief angle.

How do the cutting and clearance angles affect our finishing? Paul Seller has suggested grinding the back bevel of a BD plane for those rare occasions that he needs a higher cutting angle.

Originally Posted by IanW

I'd like to do a bit of a straw poll:

1. How many of you out there regularly use 38* bevels on BU planes for planing any significant areas?
2. Of those who have bought a second blade, how often do you actually change it?
Cheers,

I actually own a veritas small smooth BU plane, with 2 irons, one with 38° PMV-11 iron and one 25° degree. I have never used the 25° bevel. I bought the plane with 2 irons and I only use the higher bevel-angle one.

Originally Posted by justonething

One of the reasons that I want to buy a replacement plane iron is that my #7 BU plane came with an A2 blade and I am keen to lay my hands on a PMV-11 iron. I might as well buy a higher bevel iron while keeping the 25° iron for mitre and end grain use.

It seems that 38° is a good compromise and I can always put on a micro-bevel if I want to....

Well, a 50 degree cutting angle, which is what your 38* bevel gives you, isn't that much different from the standard 45 degree BD so probably involves little more effort to push around. The effort seems to start climbing more noticeably to me as the bed angle approaches 55* on a BD plane. Keeping the high angle on the A2 blade is a sensible choice, that stuff does not like acute bevels at all when forced to eat our hard woods, whereas the PM blades work very happily at the old typical grind/hone angles. But on a jointer, I think I'd be using the PM blade as my regular blade & only fitting the A2 when I needed a higher cutting angle.

Originally Posted by justonething

.... In the discussions. I could see that the way that BU plane deals with difficult material by lifting the effective cutting angle while keeping the relief angle constant at some 12°. On a BD plane, the effective cutting angle is set at 45°, but one could tries to reduce tearing by reducing the relief angle.

How do the cutting and clearance angles affect our finishing? Paul Seller has suggested grinding the back bevel of a BD plane for those rare occasions that he needs a higher cutting angle.....

Clearance angle has little effect on finish, it's there to allow freer penetration of the cutting edge in a somewhat elastic material. BU planes have a fixed clearance (= bed angle) and it's only a concern on BD planes if you put bevels >38* on them.

There is a little more to it than just the angle at which the front of a plane blade meets the wood. You can only compare cutting angles on BU planes with 'single-iron' BD planes, because the cap-iron is a big game-changer. Even when set "rank" (i.e. 0.5-0.8mm back from the cutting edge), a cap iron can have a big effect, especially with thicker shavings. To get the maximum control with fine shavings you need to set the cap-iron closer. In something exceeding 90% of cases, a 45* BD plane with a well-set cap-iron out-performs any BU plane (unless, maybe, you raise the cutting angle to an absurd degree - just an idea, I'll leave it to someone else to test that!).

Putting back-bevels on BD blades increases effective cutting angles, and of course it works, to an extent, but if you do that you are effectively changing your plane to single-iron mode & making the cap-iron redundant! You will almost certainly get a better result by making full use of the cap-iron. To put it simply, a close-set cap-iron raises the cutting angle even further than a back-bevel. Typically, it meets the blade surface at a tangent of ~45* or more, so if the edge of the cap-iron is close enough to the cutting edge you have an effective cutting angle at least 90*. Provided the shaving is turned sharply within the limits of its beam-strength, you are combining the benefit of a 'sharp' cutting edge meeting the wood at a low entry-angle, with the fibre-curling effect matching that of a scraper - the best of all possible worlds. You can match or even better the performance with a scraper plane, but the wear-rate on a scraper edge is high because the metal of a scraper blade is kept deliberately softer than a typical plane blade by a good margin. Even though burnishing the edge work-hardens the blade to a degree, it won't maintain peak performance anywhere near as long as a good plane blade. Furthermore, even 'thick' shavings off a scraper are very fine, so they are painfully slow compared with a conventional plane.

In summary, a standard pitch BD plane with a close-set cap-iron simply has a higher (effective) cutting-angle than the highest (practical) angle you can put on a BU blade. In certain situations, it will out-perform any BU plane you can bring to the picnic, but I would never bet money on it because for reasons I've yet to understand, & probably never will, my 60*, single iron infill will sometimes beat all-comers. But if any of your BU planes, with any blade bevel angle, can regularly put a surface as good as my little 45* smoother managed on this ringed-Gidgee I'd be pleasantly surprised: planed gidgee.jpg

Cheers,

That was very nicely put, Ian.

I know that some - myself included - have likened the closely set chipbreaker to a high cutting angle, but I do not know of any research that has evidence for this as you commented here .. “In summary, a standard pitch BD plane with a close-set cap-iron simply has a higher (effective) cutting-angle than the highest (practical) angle you can put on a BU blade”.

The K & K video, as far as I can recall, does not suggest this, only illustrates the shavings being lifted closer to the blade.

The signature of a closed chipbreaker is a straight shaving (as opposed to one that curves up into a roll). This is also the hallmark of a high cutting angle. So it is not difficult to make that extrapolation. But is it correct?

Regards from Perth

Derek

Originally Posted by derekcohen

..... The signature of a closed chipbreaker is a straight shaving (as opposed to one that curves up into a roll). This is also the hallmark of a high cutting angle. So it is not difficult to make that extrapolation. But is it correct?....

Well Derek, as an ex-pathologist, I used plenty of weasel words like "seems" & "appears" to try & cover the bases.

I really don't know, but it seems like a useful working hypothesis, and it ties together the common effect of high cutting angles & chip-breakers. However, as we have both stated, there is a difference in practice between high bed angles & use of a cap-iron. It may simply be due to the fact that a close-set cap-iron gives an even higher effective cutting angle than a 60* bed, but I think I'll leave it to someone else to figure out the precise parameters...

Cheers,